Physicochemical Properties And Processing Adaptability Of Apios Fortunei And Preparation Of Extruded Rice

Apios is native to America,and its root tuber is a staple food with a history of 100 years.Shan County of Shandong Province is the leading producer of Apios fortunei in China.The root tuber of A.fortunei is rich in nutrition.The main component is starch and the content of protein is high.In addition,it has a variety of flavonoid substances and trace elements.A large number of studies focused on its active ingredients and functional characteristics,but few studies were made on the physicochemical properties and processing characteristics of its powder and main ingredient starch,which limited the application of A.fortunei resources.In order to expand the utilization of A.fortunei resources,the powder and starch of A.fortunei root were studied in this paper.Firstly,the physical and chemical properties of A.fortunei powder and its starch were compared with those of corn starch and potato starch.The results showed that A.fortunei in China had the highest starch content in the genus Apios,and its amylose content(17.49%)was higher than that of corn starch and potato starch.Scanning electron microscope(SEM)and particle size distribution showed that the whole powder of A.fortunei was coarse and the particle size distribution was uneven.Tuer starch granules were smooth,with the smallest particle size(8.48μm)and uniform particle size distribution.X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(ATR-FTIR)showed that the whole powder and starch were C_A-type crystal with low short-range order.A.fortunei powder has the highest solubility and the lowest swelling power.Before 75℃,its solubility and swelling power were close to those of corn starch,and after 75℃,they all increased significantly.The freeze-thaw stability of A.fortunei starch was poor.The thermal characteristic curve of A.fortunei powder and starch had two peaks,and the retrogradation degree of A.fortunei starch was 36.40%.The transparency,sedimentation stability,viscosity,gel strength,thixotropy,storage modulus and loss modulus of A.fortunei powder were the lowest,and these properties of starch were between corn starch and potato starch.The digestibility of A.fortunei powder was similar to that of corn starch,and the content of resistant starch of A.fortunei starch was 79.43%.Secondly,four thermal processing methods(cooking,microwave heating,baking and extrusion)were used to study the processing suitability of the A.fortunei powder and starch.SEM showed that microwave and baking had little effect on the particle morphology,while extrusion and cooking had great damage to the particle morphology.XRD and ATR-FTIR showed that the crystallinity of powder and starch decreased after thermal processing,and V-shaped crystal was produced after extrusion and cooking of powder,and the crystallinity of starch was the lowest after extrusion.The water solubility of extruded starch was the best at all temperatures,and the solubility of extruded starch was 65.12%at 45℃.The transparency of extruded starch was the highest,and that of baked starch was the lowest.The coagulation stability of extruded powder and starch was the highest.After heat treatment,the freeze-thaw stability of the powder decreased.And the samples of baked and microwave had two endothermic peaks,but the first peak was weak.After cooking and extrusion,the double peaks of the powder disappeared into single peak,andΔH_G decreased,extrusion and cooking had the greatest influence on the thermal characteristics.The gelatinization characteristics showed that the viscosity of powder and starch after hot processing decreased,the starch after baking was the easiest to retrogradation,and the starch after extrusion was not easy to retrogradation.The rheological results showed that the thixotropy of powder treated by microwave was the strongest,the viscoelasticity was the strongest.And the thixotropy of powder after cooking was the worst.The thixotropy of all starch samples were weak after hot processing,and the thixotropy and viscoelasticity of extruded starch were the weakest.Different heat treatments reduced the brightness of powder and turn yellow.After baking and cooking,the color changed the most,and the whiteness of the extruded starch was the lowest(78.65).In order to expand the utilization of A.fortunei resources and provide a new application scene for A.fortunei industrial production.The quality and functional characteristics of the optimized extruded rice were compared with natural rice and two commercially available extruded rice.The results showed that the sensory evaluation,texture characteristics and cooking quality of A.fortunei extruded rice were closer to those of natural rice than those of commercial extruded rice.The active ingredients content and antioxidant activity were significantly higher than those of natural rice and ordinary commercial extruded ric.In gengral,A.fortunei extruded rice had better edible quality and higher nutritional value.The research results of this study will expand the application prospect of the AP and AS,and provide basic data and theoretical basis for the deep processing of A.fortunei resources.